Field
Implementations of the present disclosure generally relate to separators, high performance electrochemical devices, such as, batteries and capacitors, including the aforementioned separators, and methods for fabricating the same.
Description of the Related Art
Fast-charging, high-capacity energy storage devices, such as capacitors and lithium-ion (Li-ion) batteries, are used in a growing number of applications, including portable electronics, medical, transportation, grid-connected large energy storage, renewable energy storage, and uninterruptible power supply (UPS).
Li-ion batteries typically include an anode electrode, a cathode electrode, and a separator positioned between the anode electrode and the cathode electrode. The separator is an electronic insulator, which provides physical and electrical separation between the cathode and the anode electrodes. The separator is typically made from micro-porous polyethylene and polyolefin. During electrochemical reactions, i.e., charging and discharging, Li-ions are transported through the pores in the separator between the two electrodes via an electrolyte. Thus, high porosity is desirable to increase ionic conductivity. However, some high porosity separators are susceptible to electrical shorts when lithium dendrites formed during cycling create shorts between the electrodes.
Currently, battery cell manufacturers purchase separators, which are then laminated together with anode and cathode electrodes in separate processing steps. Other separators are typically made by wet or dry extrusion of a polymer and then stretched to produce holes (tears) in the polymer. The separator is also one of the most expensive components in the Li-ion battery and accounts for over 20% of the material cost in battery cells.
For most energy storage applications, the charge time and capacity of energy storage devices are important parameters. In addition, the size, weight, and/or expense of such energy storage devices can be significant limitations. The use of currently available separators has a number of drawbacks. Namely, such available materials limit the minimum size of the electrodes constructed from such materials, suffer from electrical shorts, require complex manufacturing methods, and expensive materials. Further, current separator designs often suffer from Lithium dendrite growth, which may lead to short-circuits.
Accordingly, there is a need in the art for faster charging, higher capacity energy storage devices with separators that are smaller, lighter, and can be more cost effectively manufactured.